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Friday, January 05, 2007

Interesting BH Found

As Louise often tells us, there is more to what we see in the sky than we realise! A black hole has been found at the centre of a globular cluster in the galaxy NGC 4472 by ESA. A quote from the BBC article:

"We were preparing for a long, systematic search of thousands of globular clusters with the hope of finding just one black hole," said Dr Maccarone. "But bingo, we found one as soon as we started the search. It was only the second globular cluster we looked at."

13 Comments:

Exciting news! I have always thought that globulars had to be there because of black holes or whatever else supermassive in their interior. You just have to look at one to see it plainly. I think a good working hypothesis is that ALL globulars have black holes inside. I am ashamed to say, however, that despite my longtime love for astronomy and stargazing, I know next to nothing about the current (and past) understanding of these objects... They are fun to watch, though!

Hi Tommaso! Yes, it is exciting. The article points to numerical work as the indicator that there should be NO Black Hole. This is now clearly wrong, and we do wonder about the immediate implications for cosmology.

Gee, this is wonderful! I was just predicting in the book that globulars contain a Black Hole, and now they've found one! It seems we are working down the mass scale, from BH's in galaxies to globulars to...? As far as "numerical work," those simulations are not nature. My computer says that Lara Croft can run and fight with those boobs.

Yeah. Now we just need to add everything up and compare it to the 'limit' on BH density in the conventional picture.

As a buxom gal myself I have to say that, although running and climbing are no trouble, fighting might be a bit trickier. In Karate class I was always good at the routines, but pretty lousy at combat. Mind you, these days I have more of a fighting spirit...

One wonders which is the cause and which is the effect. If every clump of stars has a black hole inside it, the natural implication is that black holes, in addition to being sinks where matter is eaten, are also sources which create matter.

The spooky radio show I listen to at night is having people call in who think that their souls are from animals. Turns out that there's a lot of people who think they're really dragons, wolves or whales.

So the host was asking if anyone thought their soul was of something boring, like a mouse, or a cockroach, etc., and finished his list of boring animals with kea. Or did he say the more likely kiwi?

Actually Kea, there is something suspicious about one sentence you quoted in the post above.

The researchers claim they found a BH "in the second globular they looked at". That seems to fight the fact that NGC4472 is a galaxy, not a cospicuous one, and the globular is also tiny (invisible in most visible light pics).

So isn't it the case that they looked for x-ray signals from the halo of NGC4472 instead, and pinpointed it as coming from a globular once they found the rapidly varying signal ?

If that is so, the sentence should be read as "we found a BH inside a globular _IN_THE_SECOND_GALAXY_WE_LOOKED_AT".

That makes the hell of a difference to me!

Let me know if you have any insight... Is their paper available anywhere ?

So isn't it the case that they looked for x-ray signals from the halo of NGC4472 instead, and pinpointed it as coming from a globular once they found the rapidly varying signal?

Yeah, I think that's almost right, Tommaso. Sorry, I haven't read the details yet, but there is some older related work (which I must look up) which definitely focuses on globular clusters by detecting correlated star motions via red and blue shifts. One can then use these motions to actually calculate the mass of the black hole at the centre.